1. Technical Field
This invention relates generally to physical management of substrates. More particularly, the present invention relates to an apparatus for simplified fixturing, tensioning, and ancillary processing of substrates for fabrication and assembly of surface mount products.
2. Related Art
Flexible and rigid substrates are utilized in many different applications, and it is often necessary to physically manage how these substrates are handled during various process steps, including, but not limited to: screening, printing or stenciling, material dispensing, component placement, soldering, and electrical testing (the various processing steps hereinafter referred to as “assembly techniques”). To accomplish various assembly techniques, the substrate(s) may be placed into a substrate carrier system. This carrier system typically comprises a frame to which the substrate may be mounted and a means to register and/or accommodate variations in the dimensions peculiar to individual substrates once mounted to the frame. One common substrate carrier system utilizes the application of external forces in conjunction with a split frame to facilitate operable substrate handling during various assembly techniques; however, it is then necessary to use additional appliances to both maintain the external forces on the substrate and apply tension on the split frame. Another carrier system comprises a frame with tooling pins and spring tensioning to stretch the substrate. However, each such carrier system must be customized, as the tooling pins and spring tensioners are set for a fixed configuration of tooling holes in a particular substrate. Yet another common substrate carrier system involves mounting the substrate material to a frame that exhibits an equal or higher coefficient of thermal expansion (“CTE”) to that of the substrate material. Thus, when heated within a limited processing temperature range, the frame material expands faster than the substrate and the substrate becomes tensioned. Yet, this thermally relative substrate carrier system often requires exotic frame materials, which can be expensive. In addition, an excessive mismatch of the CTE of the substrate material to the CTE of the frame material may also lead to breakage or distortion of the substrate or require an unreasonably limited processing temperature range. Still another known substrate carrier system involves laminating the substrate material onto a rigid frame for performing the requisite assembly techniques. This more permanent handling method, however, may limit the post-processing options because of the frame material thickness in direct overlap with the substrate that is necessary to maintain the mechanical integrity of the laminated assembly.
None of the known carrier systems described above have the ability to simultaneously tension the substrate and permit unencumbered processing of both top side and bottom side surfaces of the substrate without changing or adjusting the carrier system, or having some sort of other operator intervention. Often times the frame of a typical carrier system supports the edges of the substrate as well, thereby limiting the ability to process these same edges of the substrate. In addition, standard carrier systems are also often thick, thereby creating a hindrance to various assembly techniques, especially screening and printing.
Therefore, there exists a need for an apparatus for reliably tensioning flexible and rigid substrate to remove undesirable defects, such as wrinkles or other non-planar conditions that may be introduced as a result of fabrication, mounting, or during assembly techniques as well as provide the ability to process both sides of the substrate without operator intervention or alteration or process interrupting changing of the apparatus itself. The presently disclosed improvement allows for simplified fixturing, tensioning, and ancillary processing of flexible and rigid substrates for patterning, printing, placement, reflow, deposition, or any other processing step for both sides of the substrate.